Narcissists often carry on talking (rather, lecturing) long after their interlocutors - bored stiff and resentful - have physically departed or mentally switched off. They are shocked to discover that they have been conversing with thin air for awhile. They are equally astounded when they are abandoned or shunned by spouses, friends, colleagues, the media, their fans, or audiences.
The root of this recurrent astonishment is the narcissist's perverse object constancy.
(From the book "Malignant Self-love: Narcissism Revisited" by Sam Vaknin - Click on this link to purchase the print book, or 16 e-books, or 2 DVDs with 12 hours of video lectures on narcissists, psychopaths, and abuse in relationships: http://www.narcissistic-abuse.com/thebook.html)